1. 2007/09/17 SLAC IRENG07 1 Comment on IR Vacuum system Y. Suetsugu Pumping System without in-situ baking at z < L*

2. 2007/09/17 SLAC IRENG07 2 Layout 0-th draft of IR region (A. Seryi) L*

3. 2007/09/17 SLAC IRENG07 3 Vacuum system_1 Required pressures –z < L* : 1 ~ 5 x 10 -7 Pa (= 1 ~ 5 nTorr) –Up to 200 m from IP:  1x10 -7 Pa (= 1 nTorr) (Upstream side) L*

4. 2007/09/17 SLAC IRENG07 4 Vacuum system_2 The first consideration by O. Malyshev –Very reasonable design. –NEG coating at z < L* should be effective. However, –Baking in-situ at 180 - 200  C is indispensable to make use of the NEG coating. –Is it available? Dangerous to the detector circuit. Mechanical strength? –How about is the capacity of the NEG coating? –Gate valve before D0 (Cold) are required. Is there space? How about without in-situ baking? –Is it possible?

5. 2007/09/17 SLAC IRENG07 5 Pump system_1 Assumptions –Pre-baking before assembling should be done. –The chambers should be treated carefully after the pre-baking to avoid any contamination. –Water should be kept away as much as possible. –Thermal gas desorption rate without baking: After 10 hours evacuation: CO: 2 x10 -7 Pa m 3 /s/m 2 (~ 2 x10 -10 Torr l /s/cm 2 ) H 2 : 2 x10 -6 Pa m 3 /s/m 2 (~ 2 x10 -9 Torr l /s/cm 2 ) After 100 hours evaculation (after 4 days) CO: 2 x10 -8 Pa m 3 /s/m 2 (~ 2 x10 -11 Torr l /s/cm 2 ) H 2 : 2 x10 -7 Pa m 3 /s/m 2 (~ 2 x10 -10 Torr l /s/cm 2 ) About 20 times larger than those after baking (O. Malyshev)

6. 2007/09/17 SLAC IRENG07 6 Pump system_2 Assumptions –Distributed pumping to effectively evacuate these conductance-limited beam pipes –Use NEG strip : ST707 (SAES Getters) St707 NEG strip CO:0.1 l/s/cm 2 H 2 :1 l/s/cm 2 30 mm After some saturation

7. 2007/09/17 SLAC IRENG07 7 Pump system_3 Assumptions –QD0 = Cryopump (at 2K) –Pumping speed –P eq << P –C g = 0.1 –As a first approx. A: Area P eq : Equilibrium pressure m: mass of gas molecule T: Temperature C g : Sticking coefficient Equilibrium pressure [Pa] T [K]

8. 2007/09/17 SLAC IRENG07 8 Pump system_4 If no pump at cone region (z < L*) –NEG pump just before QD0 L* Pump Lumped pump may be OK 9 m NEG strip Ceramics support Beam channelPump channel Ex.

9. 2007/09/17 SLAC IRENG07 9 Pump system_5 Pressure distribution after 100 hours evacuation Calculated by a Monte Carlo code Some pumping are required at z < L* ! –Q = 2x10 -7 Pa m 3 /s /m 2 for CO –P (z 1x10 -6 Pa!

10. 2007/09/17 SLAC IRENG07 10 Pump system_6 For example, NEG pumps at the last 1 m of cone L* Pump 1 m

11. 2007/09/17 SLAC IRENG07 11 Pump system_7 Pressure distribution after 10 hours evacuation –Q = 2x10 -7 Pa m 3 /s /m 2 for CO –Q = 2x10 -6 Pa m 3 /s /m 2 for H 2 P > 1 x10 -6 Pa

12. 2007/09/17 SLAC IRENG07 12 Pump system_8 Pressure distribution after 100 hours evacuation –Q = 2x10 -8 Pa m 3 /s /m 2 for CO –Q = 2x10 -7 Pa m 3 /s /m 2 for H 2 P < 1 x10 -6 Pa !

13. 2007/09/17 SLAC IRENG07 13 Pump system_8 If some pumps is prepared at cone, no in-situ baking may be possible. Double strips (thick) or 4 pump channels is more effective. Wait for several days. Some space is required for pumps. Is it allowable? Pump

14. 2007/09/17 SLAC IRENG07 14 Pump system_9 Other components –Auxiliary pumps Ion pumps, rough pumps –Vacuum gauge –Bellows –SR mask? –Cooling water channel?  Heaing

15. 2007/09/17 SLAC IRENG07 15 Pump system_9 Issues to be solved –Heating by HOM or SR Cooling water channel? HOM absorber? –Gas desorption by SR Problem as Malyshev-san said SR mask? –Gas desorption by heating –Connection of beam pipe –RF shielding

16. 2007/09/17 SLAC IRENG07 16 Pump system_9 Ex